The purpose of this activity is for students to revisit Stage 4 of the Shake and Spill center. Students know the total number of counters and the number of red counters and have to determine the number of yellow counters. Students may use any method they choose. Students may count up from the red counters to the total using objects or drawings. Some students may subtract the number of red counters from the total. Students record each combination as an addition expression.

The number of counters students begin to play with (8 counters) was chosen to generate sums students may not yet know from memory. Students are likely to use counting strategies to generate these sums. If most students have shown they are not yet fluent with sums of 10, invite students to start with 10 counters instead.

It is important to use language that has the characteristics of a Put Together/Take Apart, Addend Unknown problem. Avoid adjusting the language of the activity to highlight the actions students take. For example, avoid asking “How many counters did __ cover up with the cup?” Emphasize that there are a number of counters on the table and some are red and some are yellow. Because there are no actions, students may consider counting on from the known addend to the total while others may consider counting back  from the total to the known addend. Some students may also consider representing all the counters and separating the known addend from the group. In the Synthesis, look for ways to highlight strategies students may easily connect with addition (for example, counting on) and those they may connect with subtraction (for example, counting back or removal).

• Select previously identified students to share the total counters, how many red counters they saw, and how they determined how many yellow counters.
• Annotate the objects or drawings students describe if the counting on or counting back they used is not easily visible to all students. (For example, annotate 3 under the 3 red counters students saw and 4, 5, 6, 7, 8 under the counters they use to count on. Circle the counting on numbers and record 5 to show 5 were counted on).
• “What expression did you write for this round? What do the numbers in your expression represent?”
• After each student shares, consider asking:
  • “How did ___ figure out how many counters were under the cup?”
  • “How do you see the red counters in their drawing? How do you see the yellow counters? How do you see the total number of counters?”
  • “What number would ___ write in the box?”

The purpose of this activity is for students to represent and solve Put Together/Take Apart, Addend Unknown story problems based on the game they played in the previous activity. Look for the different strategies students use as they experiment with ways to determine the unknown addend. Students should continue to use counters or drawings to represent all the counters in a problem as needed. Watch for the ways students transition to counting strategies by using objects or drawings to keep track of how many they count on. As students share in the Synthesis, highlight ways students organize their thinking to make it easier to keep track of the unknown addend in their solution.

Students use two-color counters during Lesson Synthesis.

• Reread the third problem.
• Invite previously selected students to share their strategy for solving it.
• “How did __ find how many counters were under the cup? How did __ show the answer to the problem?”